Lunar eclipse

This page was last edited on 19 November 2017, at 16:34.

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth, and moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can occur only the night of a full moon. The type and length of an eclipse depend upon the Moon's location relative to its orbital nodes.

A total lunar eclipse has the direct sunlight completely blocked by the earth's shadow. The only light seen is refracted through the earth's shadow. This light looks red for the same reason that the sunset looks red, due to rayleigh scattering of the more blue light. Because of its reddish color, a total lunar eclipse is sometimes called a blood moon.

Unlike a solar eclipse, which can be viewed only from a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of the Earth. A lunar eclipse lasts for a few hours, whereas a total solar eclipse lasts for only a few minutes at any given place, due to the smaller size of the Moon's shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full moon.

For the date of the next eclipse see the section Recent and forthcoming lunar eclipses.

Recent total eclipses
Lunar eclipse April 15 2014 California Alfredo Garcia Jr1.jpg
April 15, 2014
Lunar eclipse October 8 2014 California Alfredo Garcia Jr mideclipse.JPG
October 8, 2014
Lunar eclipse April 4 2015 greatest Alfredo Garcia Jr LA.jpg
April 4, 2015
Lunar eclipse September 27 2015 greatest Alfredo Garcia Jr.jpg
September 28, 2015

Types of lunar eclipse

Geometry of a Lunar Eclipse.svg
Schematic diagram of the shadow cast by the Earth. Within the central umbra shadow, the moon is totally shielded from direct illumination by the Sun. In contrast, within the penumbra shadow, only a portion of Sunlight is blocked.
Penumbral lunar eclipse 1999 jan 31.png
A total penumbral lunar eclipse dims the moon in direct proportion to the area of the Sun's disk blocked by the Earth. This comparison shows the southern shadow penumbral lunar eclipse of January 1999 (left) to the moon outside of the shadow (right) demonstrates this subtle dimming.

The shadow of the Earth can be divided into two distinctive parts: the umbra and penumbra. Within the umbra, there is no direct solar radiation. However, as a result of the Sun's large angular size, solar illumination is only partially blocked in the outer portion of the Earth's shadow, which is given the name penumbra.

A penumbral eclipse occurs when the moon passes through the Earth's penumbra. The penumbra causes a subtle darkening of the moon's surface. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth's penumbra. Total penumbral eclipses are rare, and when these occur, that portion of the moon which is closest to the umbra can appear somewhat darker than the rest of the moon.

A partial lunar eclipse occurs when only a portion of the moon enters the umbra. When the moon travels completely into the Earth's umbra, one observes a total lunar eclipse. The moon's speed through the shadow is about one kilometer per second (2,300 mph), and totality may last up to nearly 107 minutes. Nevertheless, the total time between the moon's first and last contact with the shadow is much longer and could last up to four hours.[1] The relative distance of the moon from the Earth at the time of an eclipse can affect the eclipse's duration. In particular, when the moon is near its apogee, the farthest point from the Earth in its orbit, its orbital speed is the slowest. The diameter of the umbra does not decrease appreciably within the changes in the orbital distance of the moon. Thus, a totally eclipsed moon occurring near apogee will lengthen the duration of totality.

A central lunar eclipse is a total lunar eclipse during which the moon passes through the centre of the Earth's shadow. These are relatively rare.


Lunar eclipse at sunrise Minneapolis October 2014.png
October 2014 lunar eclipse viewed from Minneapolis, with a partially eclipsed Moon still up after sunrise, seen as sunlight on the tree on the right.

A selenelion or selenehelion occurs when both the Sun and the eclipsed Moon can be observed at the same time. This can happen only just before sunset or just after sunrise, and both bodies will appear just above the horizon at nearly opposite points in the sky. This arrangement has led to the phenomenon being referred to as a horizontal eclipse. There are typically a number of high ridges undergoing sunrise or sunset that can see it. Although the moon is in the Earth’s umbra, the Sun and the eclipsed Moon can both be seen at the same time because the refraction of light through the Earth’s atmosphere causes each of them to appear higher in the sky than their true geometric position.[2]


As viewed from Earth, the Earth’s shadow can be imagined as two concentric circles. As the diagram illustrates, the type of lunar eclipse is defined by the path taken by the Moon as it passes through Earth’s shadow. If the moon passes through the outer circle but does not reach the inner circle, it is a penumbral eclipse; if only a portion of the moon passes through the inner circle, it is a partial eclipse; and if entire Moon passes through the inner circle at some point, it is a total eclipse.
Lunar eclipse contact diagram.png
Contact points relative to the Earth's umbral and penumbral shadows, here with the Moon near is descending node

The timing of total lunar eclipses are determined by its contacts:[3]

P1 (First contact): Beginning of the penumbral eclipse. Earth's penumbra touches the Moon's outer limb.
U1 (Second contact): Beginning of the partial eclipse. Earth's umbra touches the Moon's outer limb.
U2 (Third contact): Beginning of the total eclipse. The Moon's surface is entirely within Earth's umbra.
Greatest eclipse: The peak stage of the total eclipse. The Moon is at its closest to the center of Earth's umbra.
U3 (Fourth contact): End of the total eclipse. The Moon's outer limb exits Earth's umbra.
U4 (Fifth contact): End of the partial eclipse. Earth's umbra leaves the Moon's surface.
P4 (Sixth contact): End of the penumbral eclipse. Earth's penumbra no longer makes contact with the Moon.

Danjon scale

The following scale (the Danjon scale) was devised by André Danjon for rating the overall darkness of lunar eclipses:[4]

L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow is bluish and has a very bright rim.

Lunar versus solar eclipse

Solar lunar eclipse diagram.png
A solar eclipse occurs in the day time at new moon, when the moon is between the Earth and the sun, while a lunar eclipse occurs at night when the Earth passes between the Sun and the Moon.

There is often confusion between a solar and lunar eclipse. While both involve interactions between the sun, Earth, and moon, they are very different in their interactions.

Lunar eclipse appearance

Lunar eclipse oct 8 2014 Minneapolis 4 46am.png
A lunar eclipse occurs in two regions, an outer penumbral shadow where the sunlight is dimmed, and an inner umbral shadow, where much dimmer sunlight only exists by refraction through the Earth's atmosphere, leaving a red color. This can be seen in different exposures of a partial lunar eclipse, for example here with exposures of 1/80, 2/5, and 2 seconds.

The moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse.[5] The reddish coloration arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the air molecules and the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish color; an alternative way of considering the problem is to realize that, as viewed from the moon, the sun would appear to be setting (or rising) behind the Earth.

Lunar eclipse from moon simulation-sep 28 2015.png
From the Moon, a lunar eclipse would show a ring of reddish-orange light surrounding a dark Earth in the sky.

The amount of refracted light depends on the amount of dust or clouds in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color. This causes the resulting coppery-red hue of the moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting color.

March 1504 lunar eclipse

Eclipse Christophe Colomb.jpg
Christopher Columbus predicting the lunar eclipse.

When Christopher Columbus came to the New World—specifically, the north coast of Jamaica—he was able to use European scientific understanding to correctly predict a lunar eclipse. The event is known as the March 1504 lunar eclipse and occurred when Columbus, after he wanted to be seen as god-like, stated that he would make the moon disappear during the night of February 29, 1504. The reason Columbus wanted to prove he could make the moon disappear is because he and his crew were eating a great deal of the inhabitants' food, and the inhabitants refused to feed them anymore. Columbus was right in his prediction, for he used astronomical tables and local clocks in order to predict when the lunar eclipse would happen and was able to convince the inhabitants that he had the power to make the moon disappear and then reappear. After the inhabitants believed that Columbus was truly able to make the moon disappear, they begged him to return the moon to its previous form, and after roughly an allotted amount of time (the amount of time Columbus discerned to be how long the eclipse would last), Columbus agreed to return the moon, and the moon began to reappear. The next day, the inhabitants gave Columbus and his crew the food they desired.[6]

Lunar eclipse in culture

Several cultures have myths related to lunar eclipses or allude to the lunar eclipse as being a good or bad omen. The Egyptians saw the eclipse as a sow swallowing the moon for a short time; other cultures view the eclipse as the moon being swallowed by other animals, such as a jaguar in Mayan tradition, or a three legged toad in China. Some societies thought it was a demon swallowing the moon, and that they could chase it away by throwing stones and curses at it.[7] The Greeks were ahead of their time when they said the Earth was round and used the shadow from the lunar eclipse as evidence.[8] Some Hindus believe in the importance of bathing in the Ganges River following an eclipse because it will help to achieve salvation.[9]


Similarly to the Mayans, the Incans believed that lunar eclipses occurred when a jaguar would eat the moon, which is why a blood moon looks red. The Incans also believed that once the jaguar finished eating the moon, it could come down and devour all the animals on Earth, so they would take spears and shout at the moon to keep it away.[10]


The ancient Mesopotamians believed that a lunar eclipse was when the moon was being attacked by seven demons. This attack was more than just one on the moon, however, for the Mesopotamians linked what happened in the sky with what happened on the land, and because the king of Mesopotamia represented the land, the seven demons were thought to be also attacking the king. In order to prevent this attack on the king, the Mesopotamians made someone pretend to be the king so they would be attacked instead of the true king. After the lunar eclipse was over, the substitute king was made to disappear (possibly by poisoning).[10]


In some Chinese cultures, people would ring bells to prevent a dragon or other wild animals from biting the moon.[11] In the nineteenth century, during a lunar eclipse, the Chinese navy fired its artillery because of this belief.[12] During the Zhou Dynasty in the Book of Songs, the sight of a red moon engulfed in darkness was believed to foreshadow famine or disease.[13]

Blood moon

Due to its reddish color, a totally eclipsed moon is sometimes referred to as a "blood moon".[14] In addition, in the 2010s the media started to associate the term with the four full moons of a lunar tetrad, especially the 2014–15 tetrad coinciding with the feasts of Passover and Tabernacles. A lunar tetrad is a series of four consecutive total lunar eclipses, spaced six months apart.[15][16]

Blood Moon is not a scientific term but has come to be used due to the reddish color seen on a Super Moon during the lunar eclipse. When sunlight passes through the earth's atmosphere, it filters and refracts in such a way that the green to violet lights on the spectrum scatters more strongly than the red light. This results the moon to get more red light[17]


Lunar Eclipse at ESO 2017.jpg
Time-lapse sequence of lunar eclipse visible at ESO headquarters, 7 Aug 2017.[18]
Blood Moon.tif
Lunar Eclipse Transition

Every year, there are at least two lunar eclipses and as many as five, although total lunar eclipses are significantly less common. If one knows the date and time of an eclipse, it is possible to predict the occurrence of other eclipses using an eclipse cycle like the saros.

Recent and forthcoming lunar eclipses

Eclipses only occur during an eclipse season, when the Sun is close to either the ascending or descending node of the Moon.

Lunar eclipse series sets from 1998–2002
Descending node   Ascending node
Saros Date
Saros Date
109 1998 Aug 08
Lunar eclipse from moon-1998Aug08.png
Lunar eclipse chart close-1998Aug08.png
114 1999 Jan 31
Lunar eclipse from moon-1999Jan31.png
Lunar eclipse chart close-1999Jan31.png
119 1999 Jul 28
Lunar eclipse from moon-1999Jul28.png
Lunar eclipse chart close-1999Jul28.png
124 2000 Jan 21
Lunar eclipse from moon-2000Jan21.png
Lunar eclipse chart close-2000Jan21.png
129 2000 Jul 16
Lunar eclipse from moon-2000Jul16.png
Lunar eclipse chart close-2000jul16.png
2001 Jan 09
Lunar eclipse from moon-2001Jan09.png
Lunar eclipse chart close-2001Jan09.png
2001 Jul 05
Lunar eclipse from moon-2001Jul05.png
Lunar eclipse chart close-2001Jul05.png
144 2001 Dec 30
Lunar eclipse from moon-2001Dec30.png
Lunar eclipse chart close-2001Dec30.png
149 2002 Jun 24
Lunar eclipse from moon-2002Jun24.png
Lunar eclipse chart close-2002Jun24.png
Last set 1998 Sep 06 Last set 1998 Mar 13
Next set 2002 May 26 Next set 2002 Nov 20
Lunar eclipse series sets from 2002–2005
Descending node   Ascending node
111 2002 May 26
Lunar eclipse from moon-2002May26.png
Lunar eclipse chart close-2002May26.png
2002 Nov 20
Lunar eclipse from moon-2002Nov20.png
Lunar eclipse chart close-2002Nov20.png
Lunar eclipse May 2003-TLR75.jpg
2003 May 16
Lunar eclipse from moon-2003May16.png
Lunar eclipse chart close-03may16.png
Lunar eclipse November 2003-TLR63.jpg
2003 Nov 09
Lunar eclipse from moon-2003Nov09.png
Lunar eclipse chart close-03nov09.png
Total lunar eclipse May 4 2004-Jpeter smith.jpg
2004 May 04
Lunar eclipse from moon-2004May04.png
Lunar eclipse chart close-04may04.png
Oct 28 2004 total lunar eclipse-espenak.png
2004 Oct 28
Lunar eclipse from moon-2004Oct28.png
Lunar eclipse chart close-04oct28.png
2005 Apr 24
Lunar eclipse from moon-2005Apr24.png
Lunar eclipse chart close-05apr24.png
2005 Oct 17
Lunar eclipse from moon-2005Oct17.png
Lunar eclipse chart close-2005Oct17.png
Last set 2002 Jun 24 Last set 2001 Dec 30
Next set 2006 Mar 14 Next set 2006 Sep 7
Lunar eclipse series sets from 2006–2009
Descending node   Ascending node
Saros #
and photo
Saros #
and photo
Penumbral lunar eclipse 2006 March 14 Warrenton VA.jpg
2006 Mar 14
Lunar eclipse from moon-2006Mar14.png
Lunar eclipse chart close-06mar14.png
Partial lunar eclipse Sept 7 2006-Mikelens.jpg
2006 Sep 7
Lunar eclipse from moon-2006Sep07.png
Lunar eclipse chart close-2006Sep07.png
Red moon during lunar eclipse.jpg
2007 Mar 03
Lunar eclipse from moon-2007Mar03.png
Lunar eclipse chart close-07mar03.png
Lunar Eclipse.jpg
2007 Aug 28
Lunar eclipse from moon-2007Aug28.png
Lunar eclipse chart close-2007aug28.png
February 2008 total lunar eclipse John Buonomo.jpg
2008 Feb 21
Lunar eclipse from moon-2008Feb21.png
Lunar eclipse chart close-08feb20.png
2008 Aug 16
Lunar eclipse from moon-2008Aug16.png
Lunar eclipse chart close-2008Aug16.png
Penumbral lunar eclipse Feb 9 2009 NavneethC.jpg
2009 Feb 09
Lunar eclipse from moon-2009Feb09.png
Lunar eclipse chart close-09feb09.png
Penumbral lunar eclipse Aug 6 2009 John Walker.gif
2009 Aug 06
Lunar eclipse from moon-2009Aug06.png
Lunar eclipse chart close-2009aug06.png
Last set 2005 Apr 24 Last set 2005 Oct 17
Next set 2009 Dec 31 Next set 2009 Jul 07
Lunar eclipse series sets from 2009–2013
Ascending node   Descending node
Saros #
Saros #
110 2009 July 07
Lunar eclipse from moon-2009Jul07.png
Lunar eclipse chart close-2009jul07.png
December 2009 partrial lunar eclipse-cropped.jpg
2009 Dec 31
Lunar eclipse from moon-2009Dec31.png
Lunar eclipse chart close-2009Dec31.png
Lunar eclipse june 2010 northup.jpg
2010 June 26
Lunar eclipse from moon-2010Jun26.png
Lunar eclipse chart close-2010jun26.png
Near Greatest Eclipse 20101221 0011-crop.jpg
2010 Dec 21
Lunar eclipse from moon-2010Dec21.png
Lunar eclipse chart close-10dec21.png
Lunar eclipse June 2011 Total.jpg
2011 June 15
Lunar eclipse from moon-2011Jun15.png
Lunar eclipse chart close-2011jun15.png
Lunar eclipse by Shiny Things cropped.jpg
2011 Dec 10
Lunar eclipse from moon-2011Dec10.png
Lunar eclipse chart close-2011Dec10.png
Partial Eclipse of Moon 4th June 2012 Australia cropped.jpg
2012 June 04
Lunar eclipse from moon-2012Jun04.png
Lunar eclipse chart close-2012Jun04.png
145 2012 Nov 28
Lunar eclipse from moon-2012Nov28.png
Lunar eclipse chart close-2012Nov28.png
150 2013 May 25
Lunar eclipse from moon-2013May25.png
Lunar eclipse chart close-2013May25.png
Last set 2009 Aug 06 Last set 2009 Feb 9
Next set 2013 Apr 25 Next set 2013 Oct 18
Lunar eclipse series sets from 2013–2016
Ascending node   Descending node
Saros Viewing
Type Saros Viewing
Partial lunar eclipse 2013.04.25.jpg
2013 Apr 25
Lunar eclipse from moon-2013Apr25.png
Lunar eclipse chart close-2013Apr25.png
117 2013 Oct 18
Lunar eclipse from moon-2013Oct18.png
Lunar eclipse chart close-2013Oct18.png
Lunar eclipse April 15 2014 California Alfredo Garcia Jr1.jpg
2014 Apr 15
Lunar eclipse from moon-2014Apr15.png
Lunar eclipse chart close-2014Apr15.png
Lunar eclipse October 8 2014 California Alfredo Garcia Jr mideclipse.JPG
2014 Oct 08
Lunar eclipse from moon-2014Oct08.png
Lunar eclipse chart close-2014Oct08.png
Lunar eclipse April 4 2015 greatest Alfredo Garcia Jr LA.jpg
2015 Apr 04
Lunar eclipse from moon-2015Apr04.png
Lunar eclipse chart close-2015Apr04.png
Lunar eclipse September 27 2015 greatest Alfredo Garcia Jr.jpg
2015 Sep 28
Lunar eclipse from moon-2015Sep28.png
Lunar eclipse chart close-2015Sep28.png
142 2016 Mar 23
Lunar eclipse from moon-2016Mar23.png
Lunar eclipse chart close-2016Mar23.png
Partial lunar eclipse 2016.09.16.jpg
2016 Sep 16
Lunar eclipse from moon-2016Sep16.png
Lunar eclipse chart close-2016Sep16.png
Last set 2013 May 25 Last set 2012 Nov 28
Next set 2017 Feb 11 Next set 2016 Aug 18
Lunar eclipse series sets from 2016–2020
Descending node   Ascending node
Saros Date Type
Saros Date
109 2016 Aug 18
Lunar eclipse from moon-2016Aug18.png
Lunar eclipse chart close-2016Aug18.png
Penumbral lunar eclipse 2017.02.11.jpg
2017 Feb 11
Lunar eclipse from moon-2017Feb11.png
Lunar eclipse chart close-2017Feb11.png
Lunar eclipse of 2017 August 7 Kuwait.jpg
2017 Aug 07
Lunar eclipse from moon-2017Aug07.png
Lunar eclipse chart close-2017Aug07.png
124 2018 Jan 31
Lunar eclipse from moon-2018Jan31.png
Lunar eclipse chart close-2018Jan31.png
129 2018 Jul 27
Lunar eclipse from moon-2018Jul27.png
Lunar eclipse chart close-2018Jul27.png
134 2019 Jan 21
Lunar eclipse from moon-2019Jan21.png
Lunar eclipse chart close-2019Jan21.png
139 2019 Jul 16
Lunar eclipse from moon-2019Jul16.png
Lunar eclipse chart close-2019Jul16.png
144 2020 Jan 10
Lunar eclipse from moon-2020Jan10.png
Lunar eclipse chart close-2020Jan10.png
149 2020 Jul 05
Lunar eclipse from moon-2020Jul05.png
Lunar eclipse chart close-2020Jul05.png
Last set 2016 Sep 16 Last set 2016 Mar 23
Next set 2020 Jun 05 Next set 2020 Nov 30

See also


  1. ^ Hannu Karttunen. Fundamental Astronomy. Springer.
  2. ^ "In Search of Selenelion". Observing Blog - 2010-06-26. Retrieved 2011-12-08.
  3. ^ Clarke, Kevin. "On the nature of eclipses". Inconstant Moon. Cyclopedia Selenica. Retrieved 19 December 2010.
  4. ^ Paul Deans and Alan M. MacRobert (July 16, 2006). "Observing and Photographing Lunar Eclipses". Sky & Telescope. F+W.
  5. ^ Fred Espenak and Jean Meeus. "Visual Appearance of Lunar Eclipses". NASA. The troposphere and stratosphere act together as a ring-shaped lens that refracts heavily reddened sunlight into Earth's umbral shadow
  6. ^ Peterson, Ivars. "The Eclipse That Saved Columbus". ScienceNews. Society for Science & the Public. Retrieved 26 April 2017.
  7. ^ Littmann, Mark; Espenak, Fred; Willcox, Ken (2008). "Chapter 4: Eclipses in Mythology". Totality Eclipses of the Sun (3rd ed.). New York: Oxford University Press. ISBN 978-0-19-953209-4. Retrieved 17 December 2014.
  8. ^ Pollack, Rebecca. "Ancient Myths Revised with Lunar Eclipse". University of Maryland. Retrieved 2 October 2014.
  9. ^ Ani. "Hindus take a dip in the Ganges during Lunar Eclipse". Yahoo News. Retrieved 2 October 2014.
  10. ^ a b Lee, Jane. "Lunar Eclipse Myths From Around the World". National Geographic. Retrieved 9 October 2014.
  11. ^ Quilas, Ma Evelyn. "Interesting Facts and Myths about Lunar Eclipse". LA Times. Retrieved 2 October 2014.
  13. ^ Kaul, Gayatri. "What Lunar Eclipse Means in Different Parts of the World". Retrieved 6 October 2014.
  14. ^ Nigro, Nicholas (2010). Knack Night Sky: Decoding the Solar System, from Constellations to Black Holes. Globe Pequot. pp. 214–5. ISBN 978-0-7627-6604-8.
  15. ^ Sappenfield, Mark (13 April 2014). "Blood Moon to arrive Monday night. What is a Blood Moon?". Christian Science Monitor. Retrieved 30 May 2014.
  16. ^ "What is a Blood Moon?". Earth & Sky. 24 April 2014. Retrieved 30 May 2014.
  17. ^ "All you need to know about the 'blood moon'". theguardian. 28 September 2015.
  18. ^ "Lunar Eclipse @ ESO". Retrieved 14 August 2017.

Further reading

  • Bao-Lin Liu, Canon of Lunar Eclipses 1500 B.C.-A.D. 3000, 1992
  • Jean Meeus and Hermann Mucke Canon of Lunar Eclipses. Astronomisches Büro, Vienna, 1983
  • Espenak, F., Fifty Year Canon of Lunar Eclipses: 1986-2035. NASA Reference Publication 1216, 1989

External links

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